<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        console.log(1);// 同步代码
        setTimeout(()=>{ // 宏任务之中的立即执行
            console.log(2);
            process.nextTick(()=>{ // process 进程
                console.log(3);
            })
        },0)// 会进入event loop 异步代码 不会立马执行
    </script>
</body>
</html>